The present invention relates to an aircraft capable of vertical takeoff, similar for example to a quadcopter.
For many applications, it is desirable to have available an aircraft that can take off from a minimally small surface and thus, for example, does not require any special large-area airport. In addition, for some purposes an aircraft is required that is agile and that can be maneuvered precisely, and that preferably can hover in place with good hovering characteristics.
For example, for air monitoring and reconnaissance aircraft are used that are intended to hover over a target of interest, while, for example, being capable of recording images from the air. In an alternative application, an aircraft capable of vertical takeoff, sometimes also referred to as VTOL (Vertical Take-Off and Landing), can be used to fly to areas that are difficult for human beings or other machines to access, for example, in the context of catastrophe response interventions to enable transport of goods such as tools, food, or medications to such areas.
For such uses, inter alia, aircraft have been developed in which four or more rotors, equipped with a propeller and a motor that drives the propeller, each provide an essentially upward-directed vertical thrust in order, in this way, to cause the aircraft to lift off vertically or to hover. Such an aircraft equipped with four such rotors is also referred to as a quadcopter, quadrocopter, quadricopter, quadrotor, or flying platform. In general, such aircraft having more than three drive rotors are designated multicopters, standard variants including, in addition to quadcopters, those having three rotors (tricopter), six rotors (hexacopter), or eight rotors (octocopter). Such aircraft are usually operated in unmanned fashion and can be correspondingly small. In some cases, these aircraft are also referred to as drones.
Through slight tilting of the overall aircraft, or of one or more rotors, away from the horizontal, such aircraft can also be provided with a degree of forward drive, in that a thrust produced by the rotors is inclined away from the vertical. However, the flight speeds that can be achieved in this way are limited to relatively low speeds, typically below 200 km/h, frequently even less than 100 km/h, due to the physical boundary conditions that occur in this type of aircraft. Such a speed limitation results, for example, from the physical boundary condition that the propeller used for the drive is operated at high rotational speeds, and therefore a propeller blade moving forward in the direction of flight of the aircraft would, already at relatively low flight speeds, have to be moved almost at the speed of sound at least at its propeller blade tips, thus generating high air resistance and loud noises.
Therefore, conventional multicopters have good hovering properties—similar to helicopters, in which only a single rotor provides the necessary drive and a complicated rotor mechanism can be used together with a rear rotor for maneuvering the helicopter—but standardly achieve only relatively low travel flight speeds.
KR 10 2012 006 05 90 A describes a quadrocopter that can take off and land vertically and in which a direction of thrust of propellers can be varied in order, in this way, to enable provision not only of an upward drive, but also a forward drive for the quadrocopter.